docs: def reduce_to_unit(divider):
      """
      Reduce a repeating divider to the smallest repeating unit possible.
  
      Note: this function is used by make-div
      :param divider: the divider
      :return: smallest repeating unit possible
      :rtype: str
  
      :Example:
      'XxXxXxX' -> 'Xx'
      """
      for unit_size in range(1, len(divider) // 2 + 1):
          length = len(divider)
          unit = divider[:unit_size]
  
          # Ignores mismatches in final characters:
          divider_item = divider[:unit_size * (length // unit_size)]
          if unit * (length // unit_size) == divider_item:
              return unit
      return divider